An apparatus of this type is already known that has a housing which contains a fresh air inlet duct and at least three air outlet ducts for fresh or heated air. The outlet ducts serve respectively for air which is used for de-icing the windshield, for ventilating the cabin at the level of the fascia (this being the central or main air supply or ventilating outlet), and for delivering warm air to the lower part of the cabin, e.g. for foot warming purposes. The housing has a central bulkhead which divides the housing into two separate halves, each of which contains a separate regulating means for regulating the air temperature in that half of the housing. The central bulkhead extends at least partly into each of the outlet ducts, so that air at different temperatures from the two halves of the housing can be delivered respectively to the two front seats in the cabin, i.e. the right hand side and the left hand side of the front part of the cabin.
The de-icing outlet duct feeds at least one de-icing vent, and typically two de-icing vents, which are arranged respectively on the right and left hand sides of the windshield. The main air supply outlet duct feeds at least two outlet vents in the fascia, typically one on the right, one on the left, and a third one in the middle of the fascia. Finally the warm air or foot warming outlet duct feeds two vents which are arranged in the lower part of the cabin, one near the feet of the driver and one near the feet of the front passenger.
With that arrangement, the two occupants of the front seats, i.e. the driver and the front passenger, are each able to regulate individually the temperature of the air delivered into the cabin on their own side of the latter. This leads to improved comfort, while the air is distributed in identical ways in the two halves of the housing of the apparatus.
However, this known arrangement does involve drawbacks under certain circumstances in use. In particular, there is a problem when the occupants of the two front seats want very different air temperatures from each other. For example, if the driver wants air at a moderate temperature and the front passenger wants much hotter air, then the result will be that air delivered behind the windshield will be much hotter on the passenger's side than on the driver's side. This can lead to difficulties in ensuring proper de-icing and/or de-misting of the windshield on the driver's side, which in turn can be prejudicial to the driver's visibility through the windshield. This can be prejudicial to safety.
In the same example, the air delivered through the fascia vents will be hotter on the passenger's side than on the driver's side. This difference will manifest itself essentially at the level of the central fascia vent. Then, given a distribution configuration of the "bi-level" kind (with temperature stratification, in which the air delivered at the fascia vents is required to be cooler than that delivered into the lower part of the cabin), what happens is that air emitted from the central fascia vent emerges in the form of two layers, namely a cold upper layer and a hot lower layer. This is most uncomfortable to the occupants of the vehicle.
It is therefore desirable, at least under certain circumstances, to be able to deliver air towards the windshield and/or towards the fascia vents at a homogeneous temperature, while at the same time retaining the facility for having different air temperatures in the lower part of the cabin in the vicinity of the driver's feet and of the passenger's feet respectively. At the same time it is desirable to preserve the facility for delivering air at different temperatures as between the right and left hand sides of the fascia.